The invention relates to a method of and an apparatus for producing a composite thread formed by the association of a multiplicity of continuous glass filaments and continuous filaments of thermoplastic organic matter. The production of such a composite thread is described in U.S. Pat. No. 5,011,523. This patent describes installations comprising a spinneret from which continuous glass filaments are drawn, and a spinning head supplied under pressure with a thermoplastic organic substance and delivering organic continuous filaments. The two types of filament may take the form of sheets or sheets and thread at the time of assembly. One advantageous construction described in the '523 patent consists in enclosing the glass thread or filaments in organic filaments when they are combined. A composite thread produced in this way has the advantage of protecting the glass filaments from friction on solid surfaces with which the composite thread comes in contact. On the other hand, this arrangement does not encourage complete homogenization in the mixing of the two types of filament. Indeed, a cross-section through the composite thread shows each type of filament occupying a preferred zone, which may be a type of assembly desirable in certain applications.
Furthermore, these composite threads display an undulating pattern. This is most obvious when the threads take the form of bobbins because the bobbins undulate over their entire periphery. This undulation of the composite thread is in fact due to a shrinkage phenomenon in respect of the organic filaments which results in an undulation of the glass filaments. This phenomenon has different disadvantages. First of all, thick sleeves are needed in order to produce coils in such a way that they can withstand the banding effect exerted by the composite thread. Furthermore, unreeling the bobbin becomes very difficult due to the changes in geometry. This presentation of the thread may however be advantageous when for example it is involved in the structure of a woven material which will subsequently be used for reinforcing a curved article. The suppleness of the material, imparted by both the aptitude of the organic filaments for deformation and the undulation of the glass filaments assists its being placed in a mold. On the other hand, for the production of composite threads intended for manufacturing unidirectionally reinforced flat articles, this form of presentation is a handicap. As the filaments are not aligned in the final composite structure, their capacity for reinforcement in one specific direction is diminished.